The objective of this study was to determine if the modified weighted criteria have better psychometric properties than the ACR criteria for the classification of patients with systemic lupus erythematosus (SLE). A computerized list of all patients with the diagnosis of SLE (ICD9 code 710.0) attending an outpatient rheumatology clinic was generated and their medical records reviewed. The attending rheumatologists validated the diagnosis of SLE; this assessment was used as the gold standard to compute the sensitivity, specificity and accuracy of both the American College of Rheumatology (ACR) and the modified weighted criteria. A total of 363 patients were identified and included in the study. Ninety percent were women; the mean age was 44.0 (± 14.4) years, and 51% were Caucasians. The modified weighted criteria had a sensitivity of 90.3% and specificity of 60.4%. The ACR criteria had a sensitivity of 86.5% and specificity of 71.9%. Both methods had comparable positive and negative predictive values as well as similar overall accuracy. The modified weighted criteria allow the identification of more lupus patients for clinical or interventional studies; some of these patients, however, may not have SLE according to experienced rheumatologists.